Commitments and Contingencies - Letters of Credit and Guarantees (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Guarantor Obligations [Line Items]
2014	$ 10.8
2015-2018	5.7
After 2018	95.8
Total	112.3
Liabilities Recognized at Dec. 31, 2013	6.6
2014	10.8
2015-2018	5.7
After 2018	95.8
Total	112.3
Liabilities Recognized at Dec. 31, 2013	6.6
Tampa Electric Company [Member] | Letters of Credit [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	0
After 2018	0.7
Total	0.7
Liabilities Recognized at Dec. 31, 2013	0.1
2014	0
2015-2018	0
After 2018	0.7
Total	0.7
Liabilities Recognized at Dec. 31, 2013	0.1
TECO Coal [Member] | Fuel Purchase Related [Member]
Guarantor Obligations [Line Items]
2014	0.8
2015-2018	0.7
After 2018	4.0
Total	5.5
Liabilities Recognized at Dec. 31, 2013	1.5
2014	0.8
2015-2018	0.7
After 2018	4.0
Total	5.5
Liabilities Recognized at Dec. 31, 2013	1.5
Other Subsidiaries [Member] | Guaranty Under Sale Agreement [Member]
Guarantor Obligations [Line Items]
2014	0
2015-2018	5.0
After 2018	0
Total	5.0
Liabilities Recognized at Dec. 31, 2013	5.0
2014	0
2015-2018	5.0
After 2018	0
Total	5.0
Liabilities Recognized at Dec. 31, 2013	5.0
Other Subsidiaries [Member] | Fuel Sales And Transportation [Member]
Guarantor Obligations [Line Items]
2014	10.0
2015-2018	0
After 2018	91.8
Total	101.8
Liabilities Recognized at Dec. 31, 2013	0.1
2014	10.0
2015-2018	0
After 2018	91.8
Total	101.8
Liabilities Recognized at Dec. 31, 2013	$ 0.1